I recommend to set form elements colors and fonts as shown
in table~\vref{tab:gestaltung-von-formularelementen}.
\begin{longtable}{|l|c|c|c|}
\caption{Form element colors and fonts}
\label{tab:gestaltung-von-formularelementen}
\\
\multicolumn{4}{c}{~}\\*[-0.9em]
\hline
&&&\\*[-0.9em]\multicolumn{1}{|c|}{}&\multicolumn{1}{c|}{\textbf{Border color}}&\multicolumn{1}{c|}{\textbf{Fill color}}&\multicolumn{1}{c|}{\textbf{Font weight}}\\
\hline
\endfirsthead
\multicolumn{4}{|r|}{\textsl{Continuation}}
\endhead
\multicolumn{4}{|r|}{\textsl{to be continued}}
\endfoot
\hline
\endlastfoot
\hline
&&&\\*[-0.9em]Screen&colored&colored&bold\\
\hline
&&&\\*[-0.9em]Printout&black&white&regular\\
\hline
&&&\\*[-0.9em]Screen and Printout\footnote{if JavaScript is deactivated}&colored&white&regular\\
\end{longtable}
All form elements should be marked fully colored when shown on screen
so users can find all elements easily. For readability we choose
a bold font to show text on a colored background.

Printouts of forms are typically done on black-and-white printers.
On printout we want a black border and white filling for form elements.
The text is black on white now, so we do not need a bold font.

JavaScript must be enabled in the \textsc{pdf} viewer to change colors
and fonts before and after printing the document.

The color for marking form elements should be the same color for all
elements. We want to show black text on color-filled areas, so we should
use a light color for a good contrast.